The plant lectin concanavalin A from jack bean and the two lima bean lectins, a tetramer LBL4 and an octamer LBL8, are being studied. The relationship of the metal ion requirements and saccharide-binding activity are being examined by a variety of physical techniques. Transition metal ions such as Mn2+ and Ca2+ are necessary for inducing saccharide-binding activity in concanavalin A. A succinylated derivative of concanavalin A is being studied for metal-binding characteristics. This derivative is a well-behaved analog with properties similar to those of the native lectin. Metal ion-binding properties are being studied by magnetic resonance and fluorescence techniques. LBL4 and LBL8 binding to erythrocytes and lymphocytes have shown that those lectins bind with positive cooperativity to type A and AB erythrocytes but show no cooperativity with lymphocytes. As LBL8 is a potent mitogen, cooperativity is not important to the mitogenic response. One goal of this research is to develop these lectins for useful membrane probes.